Suprathermal Minor Heavy Ions In Saturn's Magnetosphere

Minor heavy ions, with MPQ > ~25 amu/e, have been measured at energies >~64 keV/e in Saturn's inner magnetosphere using the Cassini/MIMI/CHEMS Charge Energy Mass Spectrometer. CHEMS measures atomic and molecular ions in the mass-per-charge, MPQ, range 1-80 amu/e. The predominant minor heavy ions, N2+1 and O2+1, share general spatial characteristics with the dominant water group ions (taken as O+1, OH+1, H2O+1, and H3O+1). Using an extended collection interval (mid-2004 to 2010) for CHEMS, we have also found several rare heavy ion groups with MPQ > ~40 amu/e, at ~40, ~42-48, and ~52-58 amu/e. CHEMS cannot distinguish atomic from molecular species in this MPQ range, but possible candidates at these masses are Ar+1, CO2+1 or C3H8+1, and Fe+1 or C4H8+1, respectively. These rare heavy ions exhibit somewhat different spatial characteristics than the more abundant water group and N2+1 and O2+1 ions. The compositional characteristics of these suprathermal ion groups will be discussed in the context of recent results concerning liquid water on Enceladus and the composition of dark material on the moons and rings.